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Radar subsystem's chirp parameters setting:negative freq slope.

tiger_PL
Prodigy 20 points
Other Parts Discussed in Thread: IWR1642, IWR1443

I read many white paper about IWR1642, almost all development cases based on IWR1642 use positive freq slope.

In may project, i need chirps with both positive and negative freq slopes, for example:the first chirp has positive freq slope,the second chirp has negative freq slope.I want to know whether does IWR1642 have the ability to generate chirps with negative freq slope.

I have done the following work:

(parameters of radar subsystem are set by APIs in MSS of iwr1642， and i have make sure all parameters within the prescribed scope of the technical manuals )

1.I set a positive freq slope for chirps like the development cases in white paper, then do down-conversion on output signal of radar subsystem to get base-band signal，after  down-conversion observe the base-band signal on oscilloscope . I found the signal is a chirp signal with positive slope, so this parameter setting is working.

2.Set a negative freq slope for chirps, then do the same operations as step 1,on the oscilloscope i observed the signal is not a chirp signal, it's only a single frequency signal.

therefore,i think the Radar subsystem of iwr1642 has no ability to generate the chirps with negative freq slope. But this is just my own judgment, and i have send an email to TI's technical support, they are not sure about this too,and they suggested to communicate with users of iwr1642.

Is there any engineer meet the same situation, i want to further confirm my judgment.

 

  • 0
    TI__Guru 50240 points
    Hello,

    I've referred your question to an IWR team member and someone should have an answer for you shortly.


    Cheers,
    Akash
  • 0 in reply to Akash Gondalia
    TI__Mastermind 37500 points
    Hello,
    I used the mmwave SDK 1.1, for the IWR1443 EVM, the 1642 can have a similar setting. What I found (for me) is that in the console window at the bottom, a negative slope causes an exception. You will see in the two .cfg files, you need to move the starting Frequency for a negative slope. We do no realize a benefit with negative slope, we still have the Tx excess ramp time, and Idle time, as the synthesizer is supposed to shift back to the starting frequency.

    I will find out if a code update is available, for now if you want to test negative frequency, you will have to modify the main.c to resolve the exception reported.
    posfreq1443.cfg - saved configuration from Visualizer 1.01
    posfreq_chirp1443.PNG - .5RCS target at 3 meters
    pos_negslope_chirp_oob_v1p1.xlsx - calculation of Start Freq, and Slope to cover same RF range
    negfreq1443.cfg - modified configuration
    mmwavesdk1p1_negslopechirp_error.txt - console window last line below Sensor Start shows MSS error

    Looking at main.c, the MMWave_start was not successful.
    The hardware engineer explained that the RF synthesizer can perform positive or negative slope. We will try to find out more for this error.

    Regards,
    Joe Quintal
  • 0 in reply to Radio-Joe
    TI__Mastermind 37500 points
    Hello,
    One of the Automotive Radar apps engineers indicates that this can be done with the Radar Studio software package, you can follow the steps in the previous post, and try to generate a negative slope chirp. The starting frequenc + Chirpslope * numadcsamp/DFEout rate, must be withing the synthresizer range.

    Regards,
    Joe Quintal
  • 0 in reply to Radio-Joe
    TI__Mastermind 37500 points

    Hello,

    I used the IWR1443 EVM, (1642 would work), Devpack, TSW1400, and Radar Studio software.  I was able to get a Radar detected target at 3meters.

    I have included the Post Processing pictures, and the Radar Studio configuration files.

    posslopetest.xml - configuration file for Positive frequency slope

    negslopetest.xml - configuration file for Negative frequency slope

    posneg_slopeRadarStudio.zip

    Regards,

    Joe Quintal

  • 0 in reply to Radio-Joe
    Prodigy 20 points
    Thank you for your answer. I have try to modify configuration file（.cfg file of mmWave_Demo_Visualizer 1.0.0）， all parameters are within the synthesizer range, when run the program the main.c had no exception,but the output RF signal is a single frequency signal.
    I read your answer carefully, you mentioned 'Radar Studio software' and 'Devpack', and i have these two things, but i am not familiar with them, i want know if the Devpack is necessary to generate negative slop chirp.
    And can i get the positive and negative slop chirps in the same frame process period, for example, i want two adjacent chirps(one has positive slop,anther with negative slop) looks like a Triangle wave
  • 0 in reply to tiger_PL
    TI__Mastermind 37500 points
    Hello,
    The Devpack, and TSW1400 are used to extract the LVDS /CSI-2 data from the radar sensor EVM. The mmwave SDK software has a known deficiency for Out of Box demo/capture demo, that negative frequency slope is not supported.

    The Radar Studio package does not generate this error, I sent the file for this.

    You can have 2 different profiles for postive slope, and a separate profile for negative slope.

    You would create a chirp configuration, that references a positive slope. You would create a second chirp configuration that references the negative slope.

    You can create a frame configuration that loops over chirp1, then chirp2, to repeat the positive, and negative slope.

    Note: there is no benefit to the synthesizer stability, we return the synthesizer for each chirp/ profile used.

    Regards,
    Joe Quintal